What about: 

"Depending on your country of origin, your work may be protected by local copyright law by default at the moment of creation. If you'd like to signal to the community that you want to expressly put your work in the public domain -- i.e., relinquish your default copyright interests to it -- the Unlicense may be a good option for you. The Unlicense also includes a no-warranty statement from the widely-used MIT/X11 license that protects you by making clear that you're not providing any warranties to this public domain work."  

It's too long, maybe, but hits the main points.